U.S. Secretary of State John Kerry met with about 10 of the 51 State Department diplomats who last week wrote a cable arguing for "a more militarily assertive U.S. role" in Syria.

Department spokesman John Kirby said Kerry on June 21 thanked the authors of the "dissent channel" memo for their views and said he took them seriously. He believed it was "a good discussion" lasting about 30 minutes and "worth having," but declined further comment, Kirby said.

In the cable, the diplomats called for military strikes against President Bashar al-Assad's government to try to compel the regime to respect the cease-fire in the country's five-year civil war and negotiate a political solution to the conflict.

But President Obama since taking office has sought to avoid deeper military entanglements in the Middle East, and that principle has guided his policy toward Syria.

Obama's limited intervention has focused on fighting the Islamic State militant group that controls a swath of Syria and Iraq and which has inspired attacks on U.S. soil.